Technical Field PA1 (i) the nickel compound of the formula ##STR6## wherein: R.sup.3, R.sup.4, R.sup.5, R.sup.6, X.sup.1 and E.sup.1 are defined as above and L.sup.2 is a strongly coordinating ligand; and PA1 (ii) an acceptor compound which can react irreversibly with L.sup.2 ; and PA1 (i) the nickel compound of the formula ##STR7## wherein: PA1 compound. PA1 (i) one or more zero valent olefin-nickel compounds or pi-allyl nickel compounds, or a nickel(I) or nickel(II) compound capable of forming said compounds in the presence of a reducing agent; and PA1 (ii) the phosphorane of the formula EQU (R.sup.4).sub.3 P.dbd.C(R.sup.5)--C(O)R.sup.6 PA1 wherein: PA1 R.sup.4, R.sup.5 and R.sup.6 are defined as above, with the proviso that at least one R.sup.4 is aryl or substituted aryl, with an excess of the weakly coordinating ligand L.sup.1, defined as above. L.sup.1 may also serve as a solvent for the reaction. Specifically, said mixture and ligand L.sup.1 are mixed in the molar proportion of .gtoreq.1 mole of L.sup.1 per mole of mixture component (i), preferably about 10 to about 1000 moles of L.sup.1 per mole of (i), in a suitable solvent, and reacted at a temperature of about 0.degree. C. to about 150.degree. C., preferably at about 20.degree. C. to about 60.degree. C., for about one minute to about 72 h, at any suitable pressure, preferably atmospheric pressure. Preferably, the nickel compound (i) in the aforesaid mixture is bis(1,5-cyclooctadiene)nickel(O). The catalyst 1(b) is isolated by conventional techniques, such as by filtration or, if dissolved, by precipitation with a non-solvent or by solvent evaporation. Suitable solvents include aromatic compounds, such as benzene or toluene; alcohols, such as ethanol or isopropanol; ethers, such as tetrahydrofuran or diethylether; nitriles, such as acetonitrile or benzonitrile; ketones, such as acetone or methylphenylketone; amides, such as acetamide or dimethylformamide; esters, such as ethyl acetate or methyl benzoate; and dimethylsulfoxide. Aromatic hydrocarbons, such as toluene or benzene, are preferred. Halogen-containing solvents, such as chloroform, methyl iodide or bromobenzene, should be avoided because of possible reaction with the nickel-containing compounds.
This invention relates to the preparation of high molecular weight polyethylene in the presence of selected nickel-containing catalysts.
Background
Various nickel-containing compounds, usually in complexed form, are known in the art as catalysts for polymerizing ethylene to linear 1-olefin oligomers. Certain of these catalysts are reported to polymerize ethylene to high molecular weight polyethylene. For example, U.S. Pat. No. 3,686,159 discloses a phosphorane-complexed nickel catalyst which is reported to polymerize ethylene to a mixture of linear oligomers and linear, crystalline, high molecular weight polyethylene. This patent also discloses selected modifications wherein the catalysts are supported on solid substrates, including inorganic acidic oxides such as alumina or aluminosilicates. Keim, Angew. Chem., Int. Ed. Engl., 17, No. 6, 466 (1978) and 22, No. 6, 503 (1983) and Ann. N.Y. Acad. Sci., 415, 191 (1983), discloses a nickel-containing catalyst mixture which provides oligomers in toluene, but high molecular weight polymer in hexane under the same polymerizing conditions. Similar catalysts also provide high molecular weight polymer when equimolar amounts of (alpha-naphthyl).sub.3 P are added to the catalyst.
U.S. Pat. Nos. 4,310,716; 4,382,153; 4,293,727; 4,301,318; 4,293,502; 4,507,247; 4,472,522; 4,503,279; 4,472,525; 4,503,280; 4,487,847; and 4,482,640 and European application Nos. 128,596 and 128,597 disclose nickel-containing ethylene oligomerization catalysts. There is no disclosure as to how these catalysts can be modified to provide high molecular polyethylene.
It has been discovered that certain selected nickel-based catalysts which are known for use in the preparation of ethylene oligomers can be modified to provide high molecular weight polyethylene. Also discovered and disclosed herein are certain novel nickel-containing catalysts and their use in the preparation of high molecular weight polyethylene. These novel nickel-containing catalysts are claimed in copending application Ser. No. 787,148 which is of common inventive entity and which has been filed of even date herewith and allowed Apr. 20, 1987.